EEVblog Electronics Community Forum
Products => Dodgy Technology => Topic started by: MicroMho on March 22, 2018, 08:46:27 pm
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Noise cancelling headphones work, why not noise cancelling fans?
https://ntrs.nasa.gov/search.jsp?R=20170011224 (https://ntrs.nasa.gov/search.jsp?R=20170011224)
http://www.rotosub.com/s_products_demo.php (http://www.rotosub.com/s_products_demo.php)
I don't know if it's total BS, it looks like it can quiet a noisy fan in a narrow frequency band. It just doesn't seem like an organization with the aerodynamic knowledge and experience of NASA would need to resort to this type of thing. I could see this as some sort of wank for computer cases, similar to all the audiophool stuff out there. But NASA, really? :-[
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Noise is an important factor of human habitat on long duration space missions (i.e. extended stays on the ISS or a manned mission to Mars).
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Fan noise drive me nuts. It cone be used to knock out ambient sounds to help me sleep, only if the fan pitch is right and sounds a typical way. But, if I were stuck hearing it non-stop for years on in like in a space missing, with no ability to get out to some quiet, I would be driven nuts.
This is the reality of such things... Many people will have different tolerances, but imagine hearing the exact same whirring noise for 5 years, non-stop, and you cant turn it off, otherwise, you will get carbon-monoxide poisoning.
I know some large modern home central air system may be quite quiet and barely audible with those huge slow rotating fans. You just don't have the availability of space and allowance for the weight for such a huge single fan and ducting system on a space station/space ship until you get to the scale of a modern cruise ship design. Even then, it will still weight less and you will have multiple redundancies to use multiple small compact fans instead of a single central air system.
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https://www.newscientist.com/article/dn9379-noisy-iss-may-have-damaged-astronauts-hearing/ (https://www.newscientist.com/article/dn9379-noisy-iss-may-have-damaged-astronauts-hearing/)
NASA says the goal is for the working area to have noise levels at or below 60 decibels (dB) and sleep bunks to be 50dB. At their peak several years ago, noise levels reached 72 to 78dB in the working area and 65 dB in the sleep stations.
Haha silly NASA, can't see why they would have an interest in quiet fans, at all. /s
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large enough impeller, running at low speed, without any AC kick (hum), and you’re 90% of the way there.
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Yuo can also use those impellers designed using Humpback whale type fins, which actually are both more efficient at moving fluid, and are also quieter.
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noctua pc fans are very quiet
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+1 for the noctua!
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The cooling issues on the ISS are an interesting set of challenges given the inability to dump heat to space via convection or conduction. They use a special heat pipe arrangement, many meters long, to transfer heat to radiators and then to space.
The interior environment is a bit different as well given the lack of gravity and that complicates the heat flow cycle there as well. Given the small space for quarters and sleeping and the fact that that space is real near the occupied/work sections the noise issue is real. I'm glad the NASA is looking to improve the noise levels as space is not the most comfortable place there is.
Brian
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Seems the noise issues are a genuine concern aboard the ISS. Here's a few of articles that may be of interest.
- Noisy ISS may have damaged astronauts’ hearing (https://www.newscientist.com/article/dn9379-noisy-iss-may-have-damaged-astronauts-hearing/)
- 10 Astronaut Health Risks That Threaten Deep Space Missions (https://listverse.com/2014/12/29/10-astronaut-health-risks-that-threaten-deep-space-missions/) (scroll down to #7 for Hearing Loss)
- Lost in space: Hearing can suffer on ISS (http://dartmed.dartmouth.edu/winter05/html/disc_hearing.php)
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It just doesn't seem like an organization with the aerodynamic knowledge and experience of NASA would need to resort to this type of thing.
If you're using the phrase "resort to", you're implying that this approach has some sort of disadvantage, or that there is definitely a superior alternative approach. Yet you seem to fail to demonstrate that either of these things is true, or even provide an alternative suggestions?
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It's not that noise isn't an issue, Apollo 10 had a big problem with noise. A roll program (barbeque mode) that kept the sides of the ship from overheating in the sunlight kept firing the reaction jets causing a banging sound. When they tried to just turn the program off and let the craft just rotate freely, it wouldn't keep oriented well enough to keep a thing called gimbal lock from happening - so they had to turn it back on. Imagine day and night with the navagation banging away with the reaction jets every so often, jolting the crew.
As for pursuing a noise canceling fan - it just seems like reinventing the wheel. Maybe this will pay off, I don't know. It just seemed to me that a few things that have worked to quite ventilation system noise could have been tried.
-Finding a better blade airfoil
-Changing the fan size
-Finding ways to get duct velocities as low as possible
-Vibration dampening of the fan
-Dynamic balancing of the fan
-Fan tip to fan shroud clearance
-Blade durability, you wouldn't want something small to get sucked through the fan and shell a blade
-Bearings, these things are going to have to last for years of operation - probably with little or no lubrication and if they fail they can make lots of noise
-Motor/speed control, throttle the fan down when it's not needed and make sure the speed control doesn't make whining noises.
-Duct geometry, air flowing through a duct can make noise all on it's own - the quietest fan won't help. Ducting can also quiet a noisy fan. Imagine the possibilities with 3D printing, radiused
bends, double walls, light weight, interior surface finish control , integrated Helmholtz resonators (possibly even adjustable).
All this and possibly even doubling as a structural component to boot!
-Noise canceling headphones, they work - they're light weight - they'll quiet noise problems we can't even think of right now. Just make sure you bring enough batteries :)
-Don't use an old noisy Russian ventilation system - use a newer, quieter Russian ventilation system.
Those are just some ideas to think about as well. I don't know that a completely superior approach exists for any real life endeavor, but my guess is that there might be a lot of work an time needed to get even marginal results out of a noise canceling fan. One that could go into a spacecraft. This investment of time and money costs the investigation of some other solution, some other refinement. To me, the odds of achieving substantial results with this solution seem "dodgy" at best.
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I realize this may come as a shock to you, but there are, in fact, *multiple people* working for various NASA departments, and that multiple people are capable of researching more than one thing at a time.
You created an account just to whine about this - sour grapes your paper didn't get funding?
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I can sleep in a data center. Don't ask how I discovered this.
Ask some college students who did some crypto mining back in the day and you'll be surprised how many would say they actually sleep better with their miners running. Granted, few would run an Antminer S9 in their dorm room (that's a big reason college students mine altcoins instead nowadays), but something like an Avalon 4 or Antminer S3 works well for masking more distracting noises.
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...[snip]... something like an Avalon 4 or Antminer S3 works well for masking more distracting noises.
Your's and friend or the neighbors? :o >:D :-DD
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...[snip]... something like an Avalon 4 or Antminer S3 works well for masking more distracting noises.
Your's and friend or the neighbors? :o >:D :-DD
In the dorm or apartment, it's usually some neighbor staying up late who causes the problem. Especially if they're overweight like most Americans are and the wooden beams squeak when they walk around.
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Biggest issue they have is lack of space and the need for low mass and long life. This constrains design so that they have to use small diameter tube and also high air velocity, not helped by the 400Hz operation being very audible from the magnetostriction in the core material in pretty every electrical system. 400Hz fans are very noisy, as they are capable of moving a really large volume for the size, and this is pretty much right near the frequency humans are most sensitive to. Hard to fix easily, bigger fans and ducting all mean either larger vehicles ( much higher cost and constraints of payload fairings and launcher dimensions) or reduced interior space or reduced complexity of systems. Same for shoving in resonators or any sort of damping, it has to survive launch stress and also have a 20 year life with almost zero maintenance, as digging out something buried deep in an assembly is very difficult when you need the rest of the system to keep you alive.
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Biggest issue they have is lack of space and the need for low mass and long life. This constrains design so that they have to use small diameter tube and also high air velocity, not helped by the 400Hz operation being very audible from the magnetostriction in the core material in pretty every electrical system. 400Hz fans are very noisy, as they are capable of moving a really large volume for the size, and this is pretty much right near the frequency humans are most sensitive to.
The ISS uses HVDC power distribution, 160V/120V IIRC.
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Mount the fans outside the vessel and connect them to the inside with ducts.
I'm sure if engineered appropriately, they could be perfectly silent in the vacuum of space :)
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Mount the fans outside the vessel and connect them to the inside with ducts.
I'm sure if engineered appropriately, they could be perfectly silent in the vacuum of space :)
Think about that for a couple of minutes.
Not a good idea.
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It was tongue-in-cheek :) but I glad someone got it
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Musk is going to Mars by 2019, so he must have one designed already, just ask him. ::)
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The Soviet space program already solved this in a much cheaper, low-tech manner - just poke everyone in the ear with a sharp pencil!
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For space missions the obvious choice to kill fan noise would be to use heat pipe "technology" and let the heat dissipate into the hull of the space craft. On the other hand, if the excess heat generated by technical devices is being used to "heat" the habitat, passive radiating surfaces might be all you need. However, this could mean bigger heat sinks -> more weight -> more transportation cost.
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Would heat pipes work in zero gravity?
I thought the vapour floated up to the cold end, condensed, and ran back down to the hot end. Does that work withough gravity?
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As far as I understood how heat pipes work, the fluid transport takes place through capillary action. That’s why you can mount them in any orientation on your CPU.
In the middle of the pipe there is some mesh / wick that holds the fluid coolant which is released into the surrounding cavity when phase changing due to energy absorption. The motion and heat transfer to the cold end occurs due to the thermal gradient and liquid phase coolant flowing from the cool end to the hot end from capillary action.
But maybe we have some expert on the subject to clear things up some more. :)
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I thought the vapour floated up to the cold end, condensed, and ran back down to the hot end.
As far as I understood how heat pipes work, the fluid transport takes place through capillary action. That’s why you can mount them in any orientation on your CPU.
You're both right. Both types exist. Capillary ones (filled with newspaper or whatever) work in all orientations, gravity-fed ones (plain hollow tubes) have higher performance but only work in certain orientations.
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Space probe approaching Pluto. Suddenly, over the data link..
EEEEEEeeeeeEEEEEEEeeeeeeeEEEEEEEeeeeeEEEEEE
"Damn. We should have used a Thermaltake instead of that cheap crap!"
"Enter Noun 25, Verb 42, Execute."
"Never seen that one before. -What does it do?
"WD-40 Activate."
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Why axial fans?.. Radial fans are MUCH more quiet, especially if you have to put some pressure behind it to get it to go through ducts... :-//
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Why axial fans?.. Radial fans are MUCH more quiet, especially if you have to put some pressure behind it to get it to go through ducts... :-//
Radial fans are quieter, really? Then compare noise of same model graphics card with radial reference fan and non reference axial fans. Radial fans provide high static pressure, axial fans more airflow at low static pressure. What is best suited depends on the task.
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In the mid to late 1990s, after the Soviet Union had broken up and funding for military and science projects had significantly diminished, there were many top-notch scientists available for lectures and research. For a very affordable fee.
My company was intent on designing a very high density PSU, where heat removal is one primary concern.
They brought this Russian thermal expert, who among other things had been involved in space borne equipment.
I could not attend, but those who did found the lectures fascinating. Some of the comments that I recall are similar to comments made by previous posters: Namely that everything one takes for granted on the earth's surface, is no longer a straightforward solution in space.
Uncommon solutions to common problems were the norm.
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Namely that everything one takes for granted on the earth's surface, is no longer a straightforward solution in space.
When they dock the dragon capsule, they pressurize it, but they still enter with oxygen masks since the materials will make the air hazardous. Both from outgassing and debris separated by vibration. Then they ventilate it for some time to ensure there are not pockets of unbreathable air left.
Astronouts also require fresh air in their sleeping cabin, since otherwise they would suffocate from their own breath. Air is also weightless, and won't disperse as it does on earth by the classical though of "hot air moving upwards".
Recently a new type of wind turbine went up on Neeltje Jans (https://en.wikipedia.org/wiki/Neeltje_Jans), it has some strange fins at the end of the blades. This significantly reduces the "whoosh" sound. Fluid dynamics is strange.